In-wheel motor and electrically driven vehicle

ABSTRACT

The in-wheel motor for installation inside a wheel disk of a wheel includes: a cylindrical coil body; a coil body support member fixed to a shaft; an outer yoke that is disposed on an outer circumferential side of the coil body, and is fixed to a wheel disk; a cylindrical inner yoke that is disposed on an inner circumferential side of the coil body, and is rotatable around the shaft; and a magnet that is fixed on one of an inner circumferential face of the outer yoke and an outer circumferential face of the inner yoke, the magnet disposed to face a circumferential face of the coil body.

This application is a continuation in part of application Ser. No.13/174,583, filed Jun. 30, 2011, now U.S. Pat. No. 8,820,448 B2, whichis based on and claims the benefit of priority from Japanese PatentApplication No. 2010-152109, filed on 2 Jul. 2010, the contents of whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an in-wheel motor that drives a wheelby a motor provided inside a wheel disk of the wheel, and particularlyrelates to an electrically driven vehicle such as an electric car, ahybrid car and a power-assisted bicycle.

2. Related Art

Patent Document 1 (Japanese Unexamined Patent Application, PublicationNo. H11-262101) discloses that an iron core and a coil wound around theiron core are provided on an inner circumferential face of an outer yoke(a motor container) that is fixed to a shaft, a magnet facing the ironcore is rotatably provided to the shaft, and a current is applied to thecoil, thereby rotationally driving a wheel disk together with the shaft.The technique of Patent Document 1 discloses that the brake disk isfixed to the shaft between the wheel disk and the outer yoke.

Patent Document 2 (U.S. Pat. No. 7,735,588 B2) discloses an inventionincluding: an outer yoke fixed to a wheel disk; and an inner yoke beingrotatable relative to the outer yoke, in which an iron core and a coilwound around the iron core are fixed to the inner yoke, a magnet facingthe iron core is fixed to the outer yoke, and an electric current isapplied to the coil, thereby rotationally driving the wheel disktogether with the outer yoke. In addition, Patent Document 2 disclosesthat a base of a brake disk support is fixed to the wheel disk via ahub, a tip of the brake disk support is disposed inside the inner yoke,the brake disk is fixed to the tip of the brake disk support, and thebrake disk and a caliper are provided on an inner circumferential sideof the inner yoke.

SUMMARY OF THE INVENTION

However, in Patent Document 1, since the brake disk is provided betweenthe outer yoke and the wheel disk, space for the brake mechanisms (suchas the brake disk and the caliper) are required inside the wheel disk inaddition to the space for the motor mechanism; therefore, there is aproblem that restriction is imposed on the space for the motormechanism.

In Patent Document 2, a brake mechanism is provided on an innercircumferential side of an inner yoke, but a base of a brake disksupport is fixed to a wheel disk via a hub, and a tip thereof isdisposed on the inner yoke to fix the brake disk; therefore, there is aproblem that the configuration is complicated.

Moreover, in Patent Document 2, the brake mechanism is disposed on theinner circumferential side of the motor mechanism inside the wheel disk,but the motor mechanism and the brake mechanism are separatelyconfigured; therefore, there is a problem that restriction is imposed onthe space for the motor mechanism.

Furthermore, both Patent Documents 1 and 2 disclose a motor of a coretype in which a coil is wound around an iron core; therefore, there is aproblem that the weight is increased.

Accordingly, an object of the present invention is to provide anin-wheel motor and an electrically driven vehicle being lightweight,with a brake mechanism, without imposing any restriction on space forinstalling a motor mechanism.

In order to achieve such an object, a first aspect of the presentinvention is to provide an in-wheel motor installed inside a wheel diskof a wheel to rotationally drive the wheel around a shaft of the wheelby way of applying a current thereto, and the in-wheel motor includes: acylindrical coil body to which a lead wire for applying a current isconnected, the shaft being inserted in an inner circumferential side ofthe coil body; a coil body support member that is fixed to the shaft tosupport the coil body; a cylindrical outer yoke that is disposed on anouter circumferential side of the coil body, and is fixed to the wheeldisk; a magnet that is fixed on an inner circumferential face of theouter yoke, and is disposed to face an outer circumferential face of thecoil body; a cylindrical inner yoke that is disposed on the innercircumferential side of the coil body, and is disposed to face an innercircumferential face of the coil body, the inner yoke being fixed to theouter yoke and being rotatable around the shaft; a brake disk that isfixed to an inner circumferential side of the inner yoke; and a caliperthat is provided on the inner circumferential side of the inner yoke tobrake the brake disk.

According to the first aspect of the present invention, the motormechanism installed inside the wheel disk is a motor mechanism of aso-called coreless type without an iron core; therefore, it is possibleto provide an in-wheel motor that is more lightweight than a motor of acore type having an iron core such as those in Patent Documents 1 and 2.

It should be noted that the motor mechanism is configured with the coilbody, the outer yoke, the inner yoke and the magnet; and the brakemechanism is configured with the brake disk and the caliper.

Since the brake mechanism is disposed inside the motor mechanism, theentire space inside the wheel disk can be utilized as the motormechanism without imposing any restriction on the motor mechanism.

Since the brake disk support is directly fixed to the inner yoke as anoperation member configuring the motor mechanism, a simple configurationcan be achieved.

In the first aspect of the present invention, it is preferable that theouter yoke and the inner yoke together cover an outer circumferentialside face, an inner circumferential side face, and one edge of thecylindrical coil body.

Since the outer yoke and the inner yoke cover the coil body, it ispossible to prevent water and foreign matter from adhering thereto.

Moreover, in the first aspect of the present invention, it is preferablethat the in-wheel motor further includes a caliper support disk, towhich the caliper is mounted, and which is fixed to the shaft, in whicha vent hole is formed in the wheel disk in a position facing an endportion of the shaft, the caliper support disk is disposed to face thevent hole of the wheel disk, and an outer diameter of the calipersupport disk is larger than that of the vent hole of the wheel disk.

With such a configuration, by taking in air through the vent hole of thewheel disk, it is possible to cool the inside of the motor. The calipersupport disk faces the vent hole, and the outer diameter thereof islarger than that of the vent hole; therefore, even in a case of takingin air from outside through the vent hole, it is possible to preventwater and foreign matter from invading the inside of the motor throughthe vent hole.

It is preferable that the in-wheel motor further includes a driverconnected to the lead wire for applying a current to the coil body; anda power supply connected to the driver, in which the in-wheel motorworks as a generator such that, in a driving mode, the driver supplieselectricity from the power supply to the coil body and, in a brakingmode, the driver supplies electricity from the coil body to the powersupply.

When braking is applied to the wheel, the in-wheel motor works as agenerator to convert the rotational energy into electricity, and as aresult, the in-wheel motor can function as a regenerative brake.

A second aspect of the present invention is to provide an electricallydriven vehicle that is equipped with the in-wheel motor according to thefirst aspect of the present invention. The electrically driven vehiclerefers to an electric car, a hybrid car, a motorcycle, a power-assistedbicycle, a wheelchair, etc.

According to the second aspect of the present invention, it is possibleto provide the electrically driven vehicle that achieves effects similarto those of the first aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view showing an in-wheel motoraccording to a first embodiment of the present invention, which is cutinto half along a shaft;

FIG. 2 is a front view of a wheel disk shown in FIG. 1, which is viewedfrom outside a vehicle; and

FIG. 3 is a vertical cross-sectional view showing an in-wheel motoraccording to a second embodiment of the present invention, which is cutinto half along a shaft.

FIG. 4 is a vertical cross-sectional view showing an in-wheel motoraccording to a third embodiment of the present invention, which is cutinto half along a shaft.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the present invention is hereinafter described indetail with reference to FIGS. 1 and 2. An in-wheel motor 1 according tothe first embodiment is provided inside a wheel disk 5 of each of fourwheels of an electric automobile, and a tire 7 is attached to an outercircumference of the wheel disk 5, thereby electromotively driving eachwheel.

The in-wheel motor 1 includes: a stator disk 11 fixed to a shaft 9; acoil body 13 fixed to the stator disk 11; an outer yoke 15 disposed onan outer circumferential side of the coil body 13; a magnet 31 fixed onan inner circumferential face of the outer yoke; an inner yoke 17disposed on an inner side to the coil body 13; and a brake mechanism 16disposed on an inner circumferential side of the inner yoke 17.

In the present embodiment, a motor mechanism is configured with the coilbody 13, the outer yoke 15, the inner yoke 17, and the magnet 31.

A hollow 19 for wiring is formed inside the shaft 9, and a lead wire 21for applying an electric current to the coil body 13 passes through thehollow 19 of the shaft 9 and an inner circumferential side space of theouter yoke 15, and is connected to the coil body 13.

The stator disk 11 as coil body support member is discal, in which theshaft 9 is inserted through an aperture formed in the center of the diskto be fixed to the shaft 9 with a key 12.

The coil body 13 has a cylindrical shape, in which, for example, acopper plate is etched to be formed into a linear shape that is theninsulated and superimposed as multiple layers. A car body side edge 13 aof the coil body 13 is fixed to the outer circumferential portion of thestator disk 11.

The outer yoke 15 has a cylindrical shape, in which a car body side edge15 a of the cylinder is fixed to a cover disk 29, and a car body outerside edge 15 b is bent toward the inner circumferential side. The carbody side edge 15 a of the outer yoke 15 is fixed to an outercircumferential portion 29 a of the cover disk 29 with a screw 27, andthe cover disk 29 is discal, in which an insertion hole for the shaft 9is formed in the central portion of the disk, and the shaft 9 isinserted through the insertion hole to be fixed to a bearing 25 with ascrew 30.

The car body outer side edge 15 b of the outer yoke 15 is fixed on aninner surface of the wheel disk 5 via a spacer 26. Moreover, in the carbody outer side edge 15 b of the outer yoke 15, a bent innercircumferential side edge thereof is fixed to a wheel-disk side edge 17a of the inner yoke 17.

The magnet 31 is provided to the inner circumferential face of the outeryoke 15, and the magnet 31 is disposed to face the coil body 13. Itshould be noted that the magnet 31 is polarized to have a plurality ofmagnetic poles such that the magnetic poles vary in a circumferentialdirection.

The inner yoke 17 has a cylindrical shape, and is disposed to face themagnet 31 via the coil body 13. An inner circumferential face of theinner yoke 17 is fixed to a support disk 33, and the support disk 33 isfixed to a bearing 35 of the shaft 9. It should be noted that an oilseal 34 is provided to the bearing 35.

The outer yoke 15 and the inner yoke 17 are made of a magnetic material,and form a passage for magnetic flux.

In addition, in the present embodiment, the outer yoke 15, the inneryoke 17 and the stator disk 11 surround the outer circumferential side,the inner circumference and both ends of the coil body 13, and thuscover substantially the entirety of the coil body 13.

Furthermore, the outer yoke 15, the inner yoke 17, the support disk 33and the cover disk 29 maintain the coil body 13 in a hermetically-sealedstate.

The brake mechanism 16 is configured with a doughnut-shaped brake disk37 and a caliper 39, the brake disk 37 being fixed on the innercircumferential face of the inner yoke 17. The caliper 39 is fixed to adiscal caliper support disk 41 with a screw 43, and the caliper supportdisk 41 is fixed to the shaft 9 with a spline 45.

Moreover, a vent hole 47 is formed in the wheel disk 5 in a positionfacing a car body outer side edge 9 a of the shaft 9, and the outerdiameter of the caliper support disk 41 is larger than that of the venthole 47 of the wheel disk 5.

Next, driving, operation and effect of the in-wheel motor 1 according tothe embodiment of the present invention are described.

The in-wheel motor 1 is driven in such a way that an electric current isapplied through the lead wire 21 to the coil body 13, and as a result ofan electromagnetic force arising against a magnetic field between themagnet 31 and the inner yoke 17, the magnet 31, the outer yoke 15 andthe inner yoke 17 rotate as rotors with the coil body 13 serving as astator, and the wheel disk 5 fixed to the outer yoke 15 rotates aroundthe shaft 9.

When braking is applied to the rotation of the wheel disk 5, the brakedisk 37 brakes through friction by operation of the caliper 39.

Since the in-wheel motor 1 according to the first embodiment is a motorof a so-called coreless type without an iron core, it is possible toprovide an in-wheel motor that is more lightweight than a motor of acore type having an iron core such as those in the conventional art.

The inner yoke 17 and the outer yoke 15 are integrated, and the coilbody 13 is disposed between the outer yoke 15, to which the magnet 31 isfixed, and the inner yoke 17; therefore, the outer yoke 15 and the inneryoke 17 can enhance the flux density of the magnet 31 acting on the coilbody 13, and the driving torque can be enhanced.

The brake disk 37 is fixed to the inner yoke 17 that configures themotor mechanism of the in-wheel motor 1, and the brake disk 37 isdisposed on the inner circumferential side of the inner yoke; therefore,the brake disk 37 can be disposed inside the inner yoke with a simplestructure.

Since the brake disk 37 and the caliper 39 are disposed on the innercircumferential side of the coil body 13, the brake mechanism 16 can beinstalled inside the motor mechanism, and it is not required to providespace for installing the brake mechanism 16 in addition to the space forinstalling the motor mechanism, and thus the space for the motormechanism is not restricted by the brake mechanism 16.

Since the outer yoke 15 and the inner yoke 17 cover the coil body 13, itis possible to achieve waterproofing of the coil body 13, and to preventforeign matter from adhering thereto.

Furthermore, in the first embodiment, since the outer yoke 15, the inneryoke 17, the support disk 33 and the cover disk 29 maintain the coilbody 13 in a hermetically-sealed state, it is possible to enhance theeffect of preventing water and foreign matter from adhering to the coilbody 13.

By taking in air through the vent hole 47 of the wheel disk 5, it ispossible to cool the inside of the in-wheel motor 1. Since the calipersupport disk 41 faces the vent hole 47, and the outer diameter thereofis larger than that of the vent hole 47, it is possible to prevent waterand foreign matter from invading the inside of the in-wheel motor 1through the vent hole 47.

Another embodiment of the present invention is hereinafter described,and in the embodiment to be described below, by assigning the samereference numerals to portions that achieve the same operation andeffect as the first embodiment, descriptions of such portions areomitted, and points different from the first embodiment are mainlydescribed in the following description.

A second embodiment of the present invention is described with referenceto FIG. 3. In the second embodiment, the lead wire 21 described in thefirst embodiment is connected to a driver 51, and the driver 51 isconnected to a power supply 53. The driver 51 is switched in conjunctionwith brake operation units 57 such as a brake pedal, and when a brakeoperation is performed, the driver 51 supplies electricity from the coilbody 13 to the power supply 53 to cause the in-wheel motor 1 to work asa generator.

According to the second embodiment, when braking is applied to thewheel, the in-wheel motor 1 works as a generator to convert therotational energy into electricity, and as a result, the in-wheel motor1 can function as a regenerative brake.

The present invention is not limited to the aforementioned embodiments,and can be modified in various ways without departing from the scope ofthe present invention. For example, in the first and second embodiments,the vent hole 47 of the wheel disk 5 may not be provided. Moreover, in acase in which the vent hole 47 is provided, the position thereof is notlimited to the position facing the car body outer side edge 9 a of theshaft 9, and the vent hole 47 may be provided in another position of thewheel disk 5, for example, a position spaced apart from the car bodyouter side edge 9 a of the shaft 9.

Moreover, in the second embodiment, resistance may be connected to thedriver 51 to convert the rotational energy into heat for generatingheat.

A third embodiment of the present invention is described with referenceto FIG. 4. In the third embodiment, the magnet 31 fixed on the outercircumferential face of the inner yoke 17.

In the third embodiment an outer circumferential face of the magnet 31may be wound with carbon fiber (not shown to prevent getting out bycentrifugal force.

In the third embodiment, an inertial force of rotation is smaller thanthe first embodiment, therefore response of moving and stopping isbetter than the first embodiment. Also, in the third embodiment consumedenergy is smaller than the first embodiment because of the inertialforce of rotation is smaller than the first embodiment.

What is claimed is:
 1. An in-wheel motor installed inside a wheel diskof a wheel to rotationally drive the wheel around a shaft of the wheelby way of applying a current thereto, the in-wheel motor comprising: acoreless cylindrical coil body to which a lead wire for applying acurrent is connected, the shaft being inserted in an innercircumferential side of the coil body, the coil body supported at aninner car body end by a disk-shaped coil body support member that isfixed to the shaft; a cylindrical outer yoke that is disposed on anouter circumferential side of the coil body, and an outer wheel-disk endthereof is fixed to the wheel disk, an inner car body end of the outeryoke further being fixed to a cover disk that covers an inner car bodyside of the in-wheel motor and is journalled for rotation about theshaft; a cylindrical inner yoke that is disposed on an innercircumferential side of the coil body and has an outer wheel-disk endthereof attached to the outer wheel-disk end of the outer yoke, an innercar body end of the inner yoke further being fixed to a support diskrotatable around the shaft, wherein the outer yoke, the inner yoke, thesupport disk and the cover disk together rotate as a rotor around thecoil body and provide a hermetic seal around the coil body so as toprevent water and foreign matter from reaching the coil body; a magnetthat is fixed to rotate with the rotor immediately adjacent acircumferential face of the coil body; a brake disk that is fixed to aninner circumferential side of the inner yoke; and a caliper that isprovided on the inner circumferential side of the inner yoke to brakethe brake disk.
 2. The in-wheel motor according to claim 1, wherein theouter wheel-disk end of the outer yoke includes a bent circumferentialside edge thereof fixed to the outer wheel-disk end of the inner yokeand to the wheel disk.
 3. The in-wheel motor according to claim 1,wherein the caliper is fixed to a caliper support disk which is fixed tothe shaft at a location inside of the wheel disk, and the calipersupport disk extends radially outward farther than a central vent holeformed in the wheel disk such that air may circulate to the brake disk.4. An electrically driven vehicle comprising at least one in-wheel motoraccording to claim
 1. 5. The in-wheel motor according to claim 1,wherein the magnet is fixed on an inner circumferential face of theouter yoke.
 6. The in-wheel motor according to claim 1, wherein themagnet is fixed on an outer circumferential face of the inner yoke.
 7. Amotor comprising: a coreless cylindrical coil body including tworing-shaped ends, a hollow cylindrical wall defining the two ring-shapedends and configured to encircle an external wheel shaft externallyextending into the coreless cylindrical coil body, and a lead wire forsupplying current to the coreless cylindrical coil body; a coil bodysupport member located at one of the two ring-shaped ends of thecoreless cylindrical coil body, configured to be fixed to the externalwheel shaft, and fixedly supporting the coreless cylindrical coil body;a cylindrical outer yoke including a cylindrical wall having an innerand an outer cylindrical surface, loosely fit over the corelesscylindrical coil body, and configured to be fixed to an external wheeldisk and to rotate together with the external wheel disk relatively tothe external wheel shaft; a cylindrical inner yoke including acylindrical wall having an inner and an outer cylindrical surface,loosely fit in the coreless cylindrical coil body, and configured torotate around the external wheel shaft; a magnet fixed to rotate aroundthe external wheel shaft and immediately adjacent to and directly facingthe coreless cylindrical coil body; a brake disk that is fixed to aninner circumferential side of the inner yoke; and a caliper that isprovided on the inner circumferential side of the inner yoke to brakethe brake disk.
 8. The in-wheel motor according to claim 7, wherein themagnet is fixed on the inner cylindrical surface of the outer yoke anddirectly faces an outer cylindrical wall of the coreless cylindricalcoil body.
 9. The in-wheel motor according to claim 7, wherein themagnet is fixed on the outer cylindrical surface of the inner yoke anddirectly faces the hollow cylindrical wall of the coreless cylindricalcoil body.
 10. An electrically driven vehicle comprising at least onein-wheel motor according to claim 7.